Revealing calcium ion behavior during anaerobic phosphorus release process in aerobic granular sludge system

• Published in: Bioresource technology Vol. 369; p. 128474
• Main Authors: Wang, Jixiang, Li, Zejiao, Wang, Qian, Chen, Xingyu, Lei, Zhongfang, Shimizu, Kazuya, Zhang, Zhenya, Adachi, Yasuhisa, Lee, Duu-Jong
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.02.2023
• Subjects: Anaerobiosis; Bioreactors - microbiology; CaCO3 dissolution; Calcium; Calcium release; Ion exchange; Magnesium release; Nitrogen; Phosphorus; Sewage - microbiology; Waste Disposal, Fluid; Calcium release; Ion exchange; Magnesium release; CaCO3 dissolution; CaCO dissolution
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2022.128474

[Display omitted] •Ca2+ release was detected with P release during the non-aeration phase.•Dissolution of CaCO3 contributed to Ca2+ release due to decrease in liquid pH.•Ca2+ inside granules can be reversibly exchanged with anaerobically released Mg2+. Calcium ions (Ca2+) are important for biological phosphorus (P) removal from wastewater, but its behavior has not been well documented during the anaerobic P release process. This study is aimed to explore the mechanisms of Ca2+ release in bacterial aerobic granular sludge (AGS) system. During the non-aeration (anaerobic) phase, nearly 40 % increase in Ca2+ concentration was detected at the bottom of AGS reactor where decrease in pH and increase in Mg2+ concentration occurred. The pH decrease due to anaerobic P release caused CaCO3 dissolution inside the granules, leading to Ca2+ release. In addition, the increased Mg2+ ions from hydrolysis of polyphosphates were detected to reversibly exchange with Ca2+ in granules at a molar ΔCa/ΔMg ratio of 0.51–0.65. Results from this work revealed that dissolution of CaCO3 and ions exchange between Ca2+ and Mg2+ were the two major contributors to Ca2+ release during anaerobic P release process.